1. Field of the Invention
The present invention relates to a laser treatment apparatus for treating an affected part of a patient by irradiating the part with a treatment laser beam emitted from a laser source.
2. Description of Related Art
Conventionally, a laser treatment apparatus for treating an affected part of a patient adjusts a visible aiming beam to the affected part and then emits a treatment laser beam to the aiming part. In a laser apparatus provided with a laser source that emits a visible treatment laser beam, the apparatus being used in ophthalmology and dermatology, the treatment laser source is also used for emitting an aiming beam by reducing the light quantity or another laser source (for example, a semiconductor laser) is provided to emit an aiming beam which is aligned coaxially to the treatment laser beam.
Such the laser apparatus is generally provided with a protector for protecting operator's eyes from reflection laser beams reflected by a lens or patient's eye. If using the aiming beam and the treatment laser beam that have the same color (i.e., substantially the same wavelength region), the conventional treatment apparatus uses a system to insert an operator protection filter on an observation optical path at laser irradiation time, while to move the filter off the observation optical path at patient eye observation time.
However, this filter insertion system causes problems that the operator and the patient could not concentrate their attention on the treatment operation due to frequent inserting and removing operations and noise caused by such the operations.
On the other hand, in a treatment laser apparatus separately provided with a treatment laser source and an aiming light source, which emits an aiming beam having a different wavelength from a treatment laser beam emitted from the treatment laser source, a dichroic mirror is used to protect operator's eyes from the treatment laser beam and allow the operator to observe the aiming beam, without using the operator protection filter insertion system.
However, there are some cases where the difference of wavelengths between the treatment laser beam and the aiming beam causes clinical inconveniences. For example, when a laser beam with a blue or green wavelength is used for a treatment beam, the following problems may occur in an argon laser photocoagulation apparatus using an aiming beam with a red wavelength.
When the fundus diseases treatment is performed on a patient's eye affected with cataract in the crystalline lens or opacities of the vitreous, the red aiming beam is relatively easy to reach the eye fundus, while the blue or green treatment beam tends to scatter in the opacity part and does not sufficiently reach the eye fundus. Thus, the laser photocoagulation can not be achieved or only the insufficient resulting effect can be obtained.
In addition, it is known that the transmittance of the crystalline lens changes with age and it lowers with respect to the visible light of a short wavelength. This case also results in the same problems as in the above case. In such the conditions, if the operator can observe the red aiming beam which less scatters on the fundus of the patient's eye, the operator tends to consider that the laser treatment on the eye fundus can be properly conducted. However, the actual laser treatment result was often insufficient due to the above mentioned reasons.
The red aiming beam having high transmittance deeply reaches the inside of the tissue, while the blue or green treatment laser beam with a shorter wavelength than the red light much scatters and is absorbed in the tissue at a relatively shallow part. Accordingly, there is a case where the actual treatment laser irradiation result does not conform to the operator's intention at the time of observation using the aiming beam.